U.S. patent application number 11/614095 was filed with the patent office on 2008-06-26 for method and apparatus for providing radiation shielding for non-invasive inspection systems.
Invention is credited to Richard Oliver Hargrove.
Application Number | 20080149864 11/614095 |
Document ID | / |
Family ID | 39541509 |
Filed Date | 2008-06-26 |
United States Patent
Application |
20080149864 |
Kind Code |
A1 |
Hargrove; Richard Oliver |
June 26, 2008 |
METHOD AND APPARATUS FOR PROVIDING RADIATION SHIELDING FOR
NON-INVASIVE INSPECTION SYSTEMS
Abstract
Disclosed herein is a method and apparatus for providing
radiation shielding for non-invasive inspection systems. An
embodiment of the apparatus may include a radiation shield having a
plurality of slats, where each of the plurality of slats comprises
a radiation attenuating material. The radiation shield may further
include a support structure configured to hold the slats in a
non-planar shape. An embodiment of the method may include gathering
a plurality of slats, each slat comprising a radiation attenuating
material. The method may further include disposing the slats to
form a shielding curtain having a non-planar shape. The method may
also include positioning the shielding curtain to cover an opening
of a scanner.
Inventors: |
Hargrove; Richard Oliver;
(Castro Valley, CA) |
Correspondence
Address: |
GENERAL ELECTRIC CO.;GLOBAL PATENT OPERATION
187 Danbury Road, Suite 204
Wilton
CT
06897-4122
US
|
Family ID: |
39541509 |
Appl. No.: |
11/614095 |
Filed: |
December 21, 2006 |
Current U.S.
Class: |
250/515.1 ;
29/428 |
Current CPC
Class: |
G21F 1/12 20130101; G21F
3/00 20130101; Y10T 29/49826 20150115; A61B 6/107 20130101 |
Class at
Publication: |
250/515.1 ;
29/428 |
International
Class: |
G21F 3/00 20060101
G21F003/00; B23P 11/00 20060101 B23P011/00; B23P 15/00 20060101
B23P015/00 |
Claims
1. A radiation shield, comprising: a plurality of slats, each of
the plurality of slats comprising a radiation attenuating material;
and means for holding the slats in a non-planar shape.
2. The radiation shield of claim 1, wherein the non-planar shape is
a chevron.
3. The radiation shield of claim 1, wherein the means for holding
comprises: a frame; and a plurality of curtain supports coupled
with the frame.
4. The radiation shield of claim 1, wherein the plurality of slats
is laterally staggered.
5. The radiation shield of claim 1, further comprising: a second
plurality of slats configured in a non-planar shape, wherein the
second plurality of slats are longitudinally aligned with the
plurality of slats.
6. A radiation shield, comprising: a plurality of slats of
radiation attenuating material; a support structure configured to
hold the slats to form a shielding curtain having a non-planar
shape.
7. The radiation shield of claim 6, wherein the shielding curtain
comprises a plurality of longitudinally aligned slats configured to
form a chevron shape.
8. The radiation shield of claim 6, wherein the plurality of slats
are laterally staggered.
9. The radiation shield of claim 6, further comprising: a second
plurality of slats configured form a second shielding curtain
having a non-planar shape, wherein the second plurality of slats
are longitudinally aligned with the plurality of slats.
10. The radiation shield of claim 6, wherein the non-planar
shielding curtain comprises: an apex formed on a first curtain
support; and a base formed on a second curtain support.
11. The radiation shield of claim 10, wherein the first curtain
support and the second curtain support are separated by at least a
third curtain support disposed therebetween.
12. The radiation shield of claim 10, wherein the shielding curtain
is configured to form a curtain angle between an axis tangent an
apex slat and a line extending from the apex slat to a base
slat.
13. The radiation shield of claim 12, wherein the curtain angle is
about eight degrees.
14. The radiation shield of claim 9, wherein the non-planar
shielding curtain is separated by a predetermined curtain spacing
from the second non-planar shielding curtain.
15. An inspection system, comprising: a scanner; a conveyor
configured to move objects through the scanner; and a radiation
shield positioned at an opening of the scanner, wherein the
radiation shield comprises: a plurality of slats, each of the
plurality of slats comprising a radiation attenuating material; and
a support structure configured to hold the slats to form a
shielding curtain having a non-planar shape.
16. The inspection system of claim 15, wherein the shielding
curtain comprises a plurality of slats arranged to form a chevron
shape.
17. The inspection system of claim 16, wherein each of the
plurality of slats is suspended above the conveyor.
18. The inspection system of claim 16, wherein the support
structure comprises: a plurality of curtain supports arranged to be
generally parallel to each other;
19. The inspection system of claim 16, wherein each non-planar
shielding curtain comprises: an apex formed on a first curtain
support of the plurality of curtain supports; and a base formed on
a second curtain support of the plurality of curtain supports.
20. The inspection system of claim 19, wherein the apex is directed
toward an opening of the scanner.
21. The inspection system of claim 19, wherein the apex is directed
away from an opening of the scanner.
22. The inspection system of claim 16, wherein the inspection
system is an explosive detection system.
23. The inspection system of claim 16, wherein the inspection
system is a medical inspection system.
24. A method, comprising: gathering a plurality of slats, each of
the plurality of slats comprising a radiation attenuating material;
and arranging the slats to form a shielding curtain having a
non-planar shape.
25. The method of claim 24, wherein the non-planar shape is a
chevron.
26. The method of claim 24, further comprising: positioning the
shielding curtain having a non-planar shape to cover an opening of
a scanner.
Description
BACKGROUND
[0001] 1. Field of the Invention
[0002] The technology disclosed herein relates to radiation
shielding systems generally, and more particularly, to a method,
apparatus, and system for providing radiation shielding for
non-invasive inspection systems.
[0003] 2. Discussion of Related Art
[0004] Explosive detection systems and other types of inspection
systems typically use radiation-based scanners, such as x-ray line
scanners, x-ray CT scanners, and coherent x-ray scatter scanners,
to examine bags (pieces of passenger baggage) for the presence of
one or more alarm objects (explosives, weapons, illegal drugs,
contraband, product components, and the like). In certain types of
inspection systems, such as explosive detection systems, one or
more shielding curtains typically blocks the entrance and exit of
an x-ray scanner, since highly concentrated dose of high-energy
radiation from the scanner can damage human tissue if the dose is
too high. Some shielding curtains (hereinafter, "sheet curtains")
are formed of solid sections of material. More commonly,
radiation-shielding curtains (hereinafter, "strip curtains") are
formed of multiple adjoining slats, each of which is aligned with
adjacent slats to form a common plane.
[0005] FIG. 1, a sectional, perspective view of a conventional
explosive detection system (EDS) 100, provides an example of how
radiation-shielding curtains are typically arranged. In FIG. 1, a
conveyor belt 101, positioned on a base 102, extends from one end
of the EDS 100 to the opposite end of the EDS 100. The base 102
houses one or more conveyor belt motors (not shown), a computer
(not shown), and one or more components of an x-ray scanner 103. A
housing 104 rests on the base 102. A tunnel 105 formed in the
housing 104 extends from one end of the housing 104 to the opposite
end of the housing 104, and encloses the conveyor belt 101.
[0006] The x-ray scanner 103, positioned within a center portion of
the housing 104, includes a scanning area 106, into which the
conveyor belt 101 introduces one or more scannable objects.
Configurations of the scanning area 106 will vary depending on the
type of x-ray scanner used. For example, if an x-ray CT scanner is
used, the scanning area 106 will be enclosed by a circular, movable
gantry, to which an x-ray source and one or more detectors are
fixedly attached.
[0007] Multiple, closely-spaced, strip curtains 107 hang suspended
within the housing 104 over a portion of the conveyor belt 101. The
portion of the conveyor belt over which the strip curtains 107 are
positioned extends from an entrance 108 of the EDS 100 to an
entrance 109 of the scanning area 106. In a like manner, parallel,
planar rows of strip curtains 110 hang suspended within the housing
104 over another portion of the conveyor belt 101. This other
portion of the conveyor belt 101 extends from the exit 111 of the
scanning area 106 to the exit 112 of the housing 104.
[0008] In use, pieces of luggage (hereinafter, "bags") may be
loaded onto the conveyor belt 101 at the entrance 108 of the tunnel
105. Supported by the conveyor belt 101, the bags proceed through
the EDS 100 in the direction of arrow 113 (from the EDS 100
entrance 108 to the EDS 100 exit 112). Enroute through the EDS 100,
each bag passes through the scanning area 106 and is scanned by the
x-ray scanner 103. After being scanned, the bags are transported by
the conveyor belt 101 to the EDS 100 exit 112 and ejected from the
EDS 100.
[0009] Aligning strip curtains in a common plane in the
conventional manner, as shown in FIG. 1, has disadvantages. Chief
among such disadvantages is that bags occasionally jam as they pass
through the shielding curtains. When shielding curtains are
arranged in parallel, planar rows, jamming occurs because most or
all of the slats will contact a bag simultaneously, which traps the
bag(s) in the strip curtain(s) even though the conveyor belt
supporting the bag(s) continues to move. Another disadvantage
associated with conventional strip curtains, such as those
illustrated in FIG. 1, is that the slats from one strip curtain
often entangle the slats of one or more other strip curtains.
[0010] One or more solutions are needed, which attenuate radiation
produced by a radiation-based scanner while simultaneously
permitting objects to enter and exit the scanner without
jamming.
BRIEF DESCRIPTION
[0011] Embodiments of the invention overcome the disadvantages
associated with the related art and meet the needs discussed above.
For example, embodiments of the invention provide a radiation
shield, and configurations thereof, that permit bags or other
scannable objects to enter and exit a radiation-based scanner
without jamming, while simultaneously confining radiation to a
scanning area of the scanner.
[0012] Relatively simple and cost-effective to manufacture and
install, shielding curtains constructed and configured in
accordance with embodiments of the present invention provide
advantages that render them suitable for use in security
applications, manufacturing applications, medical applications,
etc. The solutions provided by such shielding curtains, and
configurations thereof, afford several advantages, or technical
effects. Illustratively, these advantages include, but are not
limited to, significantly fewer bag jams, increased baggage
throughput, reduced maintenance costs, and/or operating costs--all
as compared with conventional shielding curtains and conventional
shielding curtain configurations.
[0013] Embodiments of the invention increase baggage throughput by
creating rows of non-planar passive shielding curtains. Each
non-planar passive shielding curtains may comprise any suitable
geometric shape. In one embodiment, each non-planar passive
shielding curtain comprises slats of radiation-attenuating material
arranged in a chevron-shape. The chevron configuration has at least
two advantages. First, a chevron configuration reduces the number
of slats that simultaneously contact a bag as the bag moves through
the shielding curtain. The chevron configuration also reduces the
force of the initial impact of the bag as it moves through the
curtains and therefore reduces the occurrence of bag jams while
still providing radiation protection. Reducing or eliminating the
number of bag jams in this manner increases the number of bags a
radiation-based inspection system can process in a given amount of
time.
[0014] Many factors will affect the bag jam rate. Exemplary factors
include, but are not limited to: whether the apex of the non-planar
radiation shield is directed toward a scanning area or toward a
portal through which bags enter or exit the scanner; the degree of
the curtain angle; how many rows of shielding curtains will be
used; how far apart the curtain rows are spaced from each other;
and the height, weight, and width of the slats used to form each
shielding curtain. In an embodiment of the invention, at least one
or more of these exemplary factors is optimized to reduce the
occurrence of bag jams.
[0015] Shielding curtains constructed and configured in accordance
with embodiments of the invention may attenuate any known type of
radiation. Non-limiting examples of the types of radiation that may
be attenuated include: X-ray radiation, microwave radiation, laser
radiation, and the like.
[0016] An embodiment of the invention provides a novel radiation
shield. The radiation shield may include a plurality of slats, each
comprised of a radiation attenuating material, and a support
structure (or means for holding). The support structure (or means
for holding) may be configured to hold the slats in a non-planar
shape.
[0017] Another embodiment of the invention provides a method of
constructing and/or installing a novel radiation shield. The method
may include: gathering a plurality of slats, each comprised of a
radiation attenuating material; disposing the slats to form a strip
curtain having a non-planar shape; and positioning the strip
curtain to cover an opening of a scanner.
[0018] The foregoing has outlined rather broadly the features of
embodiments of the invention so that the following detailed
description may be better understood. Additional features and
advantages of various embodiments of the invention that form the
subject matter of the appended claims are described below.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] For a more complete understanding of the technology
described herein, and the advantages thereof, reference is now made
to the following descriptions taken in conjunction with the
accompanying drawings, in which:
[0020] FIG. 1 is a sectional, perspective view of a conventional
explosive detection system illustrating the layout and components
of the explosive detection system;
[0021] FIG. 2 is a top view of a radiation shield configured
according to an embodiment of the invention;
[0022] FIG. 3 is a perspective view of a radiation shield
configured according to another embodiment of the invention;
[0023] FIG. 4 is a perspective view of a radiation shield
configured according to another embodiment of the invention;
[0024] FIG. 5 is a perspective view of an exemplary x-ray based
scanner for use with a non-invasive inspection system, which may be
configured to include one or more non-planar radiation shields;
[0025] FIG. 6 is a block schematic diagram of a scanner that may be
used in an inspection system, which is configured according to an
embodiment of the invention; and
[0026] FIG. 7 is a flowchart of an embodiment of a method of
constructing and configuring a radiation shield.
DETAILED DESCRIPTION
[0027] Reference is made herein to the accompanying drawings
briefly described above, which show by way of illustration various
embodiments of the invention. Persons of ordinary skill in the
above-referenced technological field will recognize that other
embodiments may be utilized, and that various changes may be made
without departing from the scope of the claimed invention.
[0028] As used herein, an element or step recited in the singular
and proceeded with the word "a" or "an" includes plural elements or
steps, unless exclusion of such plural elements or steps is
explicitly recited.
[0029] FIG. 2 is a top view of an embodiment of a radiation shield
having four strip curtains, each arranged in a non-planar shape.
Any type of non-planar (e.g., three-dimensional) shape may be used,
a non-limiting example of which is a chevron-shape. As used herein,
"chevron-shape" refers to a "V," "U," inverted "V," or inverted "U"
arrangement of radiation shielding material. As used herein,
"radiation shield" refers to any configuration of radiation
attenuating material configured to attenuate an amount of radiation
leakage and/or scatter radiation that may occur during operation of
a radiation-based scanner. The term "scanner" refers to any type of
hardware and/or related software (i.e., linear x-ray, computed
tomography (CT), coherent x-ray scatter, laser, magnetic resonance
imaging (MRI), etc.) configured to generate a digital
representation of an object for storage in a computer-readable
medium and/or for analysis by a computer. The term "strip curtain"
refers to a grouping of slats of radiation attenuating material.
The term "radiation attenuating material" refers to any material
that absorbs or reflects radiation including, but not limited to,
aluminum, antimony, bismuth, barium, cadmium, copper, iron, iodine,
lead, mercury, nickel, silver, thallium, tantalum, tellurium, tin,
tungsten, uranium, and zinc, either alone or in combination. The
term "slat" refers to a thin piece of radiation attenuating
material having a length greater than its width.
[0030] Referring to FIG. 2, a radiation shield 200 includes a
plurality of flexible (or semi-flexible) slats of radiation
attenuating material 214, and means for holding the flexible slats
214 to form a strip curtain (202, 203, 204, and 205) having a
non-planar shape. In an embodiment, the holding means comprises a
frame 201 and a plurality of curtain supports 212 from which one or
more non-planar strip curtains 202, 203, 204, 205 hang. In an
airport security application or an engineering application, the
non-planar strip curtains may be suspended over a conveyor belt
206, which may move objects in either direction indicated by the
double-ended direction arrow 230. Also as used herein, "object"
refers to anything that can be imaged by a scanner. Non-limiting
examples of an "object" include a bag, a medical patient, a
commercial product, etc. The term "bag" refers to a piece of
baggage, and the term "baggage" refers to all of a traveler's
luggage and personal belongings.
[0031] In a medical application, the non-planar strip curtains 212
may be suspended over a portion of a support structure that
supports a medical patient (or a portion thereof). Non-limiting
examples of a support structure include a bed, a table, a
stretcher, a gurney, etc. As used herein, "gurney" refers to a
mobile bed with wheels designed for transport of patients in
hospitals and ambulances.
[0032] Referring again to FIG. 2, the frame 201 may include two
substantially parallel, longitudinally extending beams 207 and 208.
The beams 207,208 may be braced with one or more lateral support
members 209. Any type of known means for fastening (e.g., a weld, a
bolt, screw, etc.) can be used to couple the lateral support
member(s) 209 with one of the beams 207 and 208. The frame 201 may
further include two upright support members 210 and 211, which
support the beams 207 and 208 above the conveyor belt 206.
[0033] The frame 201 may further include one or more curtain
supports 212, which, in an embodiment, may be cylindrical rods that
lie orthogonally across the beams 207 and 208. Each curtain support
212 may fixedly or adjustably couple with the beams 207 and 208. In
turn, an upper end of each slat 214 may couple with one of the
curtain supports 212 via one or more fasteners 213.
[0034] Each non-planar strip curtain 202, 203, 204 or 205 may
include multiple curtain supports 212. For example, in one
embodiment, each non-planar strip curtain 202, 203, 204, and 205
includes eight curtain supports 212. In other embodiments, the
number of curtain supports 212 included in each non-planar strip
curtain 202, 203, 204, and 205 may be greater or less than
eight.
[0035] Each slat 214 may comprise any radiation attenuating
material or combination of materials known to a skilled artisan.
Such a material may have a unique radiation transmission
attenuation factor, which will vary depending upon the specific
embodiment. In an embodiment, the radiation attenuating material is
generally flexible to permit each slat 214 to flex slightly when
pushed by a bag. In alternative embodiments, the radiation
attenuating material may be weighted and/or rigid.
[0036] Referring again to FIG. 2, each non-planar strip curtain
202, 203, 204, and 205 includes a base 215 and an apex 216. In an
embodiment, the base 215 is formed by two co-planar slats, and the
apex 216 is formed either by a single slat or by two co-planar
slats. The base 215 is distinguished from the apex 216 in that the
two co-planar slats that form the base 215 are separated by a
greater lateral distance (as measured orthogonally to a
longitudinal center axis 240) than the co-planar slat(s) that form
the apex 216. Additionally, the base 215 is vertically separated
(as measured along the longitudinal center axis 240) from the apex
216. When configured in this manner, each non-planar strip curtain
202, 203, 204, and 205 has a height (measured orthogonal to the
conveyor belt 206), a width (measured parallel to a width of the
conveyor belt 106), and a depth (measured along the longitudinal
center axis 240 from a plane passing through the base slats to a
plane passing through the apex slat(s)).
[0037] The chevron-shape of each strip curtain 202, 203, 204, and
205 is formed by arranging slats 214 in a predetermined pattern
such that the slats 214 are generally longitudinally aligned (as
measured along the longitudinal center axis 240) and laterally
staggered (as measured orthogonal to the longitudinal center axis
240).
[0038] In an embodiment, "longitudinally aligned" refers to one of
two arrangements of slats. In a first arrangement, the centers of
slats in one shielding curtain are generally aligned with the
centers of slats in a second (adjacent) shielding curtain. In a
second arrangement, the centers of slats in one shielding curtain
are offset from the centers of slats in a second (adjacent)
curtain. This second (offset) arrangement staggers the gaps (if
any) between the curtain slats from row to row to prevent the gaps
from being aligned and therefore reduce radiation leakage.
[0039] In an embodiment, "laterally staggered" refers to one of two
arrangements. In a first arrangement, the side edges of slats
within a shielding curtain are overlapped with each other so that
no gaps appear between neighboring curtain slats. In a second
arrangement, the side edges of slats within a shielding curtain are
not overlapped. In this second arrangement, the side edges of slats
within a shielding curtain may be separated by a gap.
[0040] In other words, one or more slats 214 forming the apex 216
may be attached to a center portion of a first curtain support 217.
A first pair of slats 221, comprised of two slats 214 that are
laterally spaced at about equal distances from the longitudinal
center axis 240 of the frame 201, may be coupled with a second
curtain support 218, which longitudinally adjoins the first curtain
support 217. A second pair of slats 222, comprised of two slats 214
that laterally spaced at greater distances from the longitudinal
center axis 240 than the first pair of strip curtains 220, may be
coupled with a third curtain support 219, and so on, until a final
pair of slats 223 having the greatest lateral spacing from the
longitudinal center axis 240 are coupled with a final curtain
support 231. In an embodiment, the final curtain support 231 is
separated from the first curtain support 217 by one or more curtain
supports disposed therebetween.
[0041] As illustratively shown in FIG. 2, such an arrangement of
slats causes a curtain angle 225 to be formed, which determines how
sharply the base 215 of each strip curtain 202, 203, 204, 205
tapers to its apex 216. Two intersecting (imaginary) lines may
define the curtain angle 225. The first line 229, which
orthogonally intersects the longitudinal center axis 240, may be
drawn tangent the apex 216. The second line 270, which passes
through the intersection of the first line 229 and the longitudinal
center axis 240, may be drawn generally along a sloping face of the
non-planar strip curtain 202 to be tangent an outer edge of one of
the pair of slats 223 that form the base 215. In an embodiment, an
exemplary curtain angle is about 8.0 degrees, but in alternative
embodiments, lesser and greater curtain angles may also be
used.
[0042] Still referring to FIG. 2, one or more predetermined curtain
spacings 226 may separate two or more of the non-planar strip
curtains 202, 203, 204, and 205 from each other. The amount of each
curtain spacing 226 will vary depending on the embodiment and the
type of application. Illustratively, the curtain spacing 226 may be
measured as the distance separating one base strip curtain 227 (in
strip curtain 205) from another adjacent base strip curtain 228 (in
strip curtain 204). In an embodiment, an exemplary curtain spacing
226 measures about 152.40 mm, but other curtain spacings are
possible.
[0043] Referring now to FIGS. 1 and 2, the apexes 216 of all or
some of the non-planar strip curtains 202, 203, 204, 205 may be
directed toward a scanning chamber 106 of a scanner 103. In such an
embodiment, the apexes 216 of all or some of the non-planar strip
curtains 202, 203, 204, 205 may be located nearer the chamber 106
than the bases 215 of each non-planar strip curtain. In alternative
embodiments, the apexes 216 of all or some of the non-planar strip
curtains 202, 203, 204, 205 may be directed away from the scanning
chamber 106 of the scanner 103. In such alternative embodiments,
the bases 215 of all or some of the non-planar strip curtains 202,
203, 204, 205 may be located nearer the chamber 106 than the apexes
216 of all or some of the non-planar strip curtains 202, 203, 204,
205.
[0044] FIGS. 3 and 4 are perspective views of embodiments of
non-planar radiation shields 300 and 400, respectively. These
views, as well as the top view shown in FIG. 2, illustrate
exemplary frames and curtain supports, which allow quick changes
from one curtain embodiment (or configuration) to another during
testing. Skilled artisans will appreciate that various other means
for supporting the novel configurations of shielding curtains
described herein (for testing and/or use in an operational medical
inspection system or explosive detection system) are possible and
contemplated. FIG. 3 is a perspective view of a radiation shield
300 having six shielding curtains 301, 302, 303, 304, 305, 306,
with each shielding curtain arranged in a chevron pattern,
according to another embodiment of the invention. Each non-planar
shielding curtain 301, 302, 303, 304, 305, 306 includes an apex 316
and a base 324, as previously described above with respect to FIG.
2.
[0045] In FIG. 3, the radiation shield 300 includes a frame 301 to
which one or more curtain supports 312 are coupled. The six
non-planar strip curtains 301, 302, 303, 304, 305, 306, each formed
of one or more slats 314, hang suspended from the one or more
curtain supports 312 over a conveyor belt 306 (or other type of
means for supporting an object for scanning). The conveyor belt 306
may be configured to move objects in either direction indicated by
the double-ended direction arrow 330.
[0046] The frame 201 may include two substantially parallel,
longitudinal beams 307 and 308 that are braced with one or more
lateral support members 309. The lateral support member(s) 309 are
attached at either end to one of the beams 307 and 308 using any
type of known fastening means (e.g., a weld, a bolt, screw, etc.).
The frame 201 may further include two upright support members 310
and 311, which support the beams 307 and 308 above the conveyor
belt 306. As noted above, the frame 201 may further include one or
more adjustable or fixed curtain supports 312, which may fixedly or
adjustably couple with the beams 307 and 308 at about right
angles.
[0047] In the embodiment shown in FIG. 3, the non-planar strip
curtains 301, 302, 303, 304, 305, 306 are paired into the following
three groups: a first curtain pair consisting of strip curtains
301,302; a second curtain pair consisting of strip curtains
303,304; and a third curtain pair consisting of strip curtains
305,306. Each of these first, second, and third curtain pairs has
an identical (or similar) internal curtain spacing 330, 331, and
332, respectively, which are further defined below. Additionally,
each of the first, second, and third curtain pairs are separated
from each other by spacings 340 and 341 (also defined further
below). For example, spacing 340 separates the first curtain pair
301,302 from the second curtain pair 303,304. Another spacing 341
may separate the second curtain pair 303,304 from the third curtain
pair 305,306.
[0048] In an embodiment, each of the internal curtain spacings 330,
331, and 332 that separate individual strip curtains are smaller
than the spacings 340,341 that separate the first, second, and
third curtain pairs.
[0049] The internal curtain spacings 330, 331, and 332 may be
measured as follows. The internal curtain spacing 330 may be the
distance between a base slat 351 of the strip curtain 301 and a
base slat 352 of the strip curtain 302. The internal curtain
spacing 331 may be the distance between a base slat 353 of the
strip curtain 303 and a base slat 354 of the strip curtain 304. The
internal curtain spacing 332 may be the distance between a base
slat 355 of the strip curtain 305 and a base slat 356 of the strip
curtain 306.
[0050] The spacings 340 and 341 between the first, second, and
third curtain pairs may be measured as follows. The spacing 340 may
be the distance between a base slat 352 of the strip curtain 302
and a base slat 353 of the strip curtain 303. The spacing 341 may
be the distance between a base slat 354 of the strip curtain 304
and a base slat 355 of the strip curtain 305.
[0051] FIG. 4 is a perspective view of a radiation shield 400
having eight strip curtains 401, 402, 403, 404, 405, 406, 407, 408,
with each strip curtain arranged in a chevron pattern that has a
predetermined curtain angle, according to another embodiment of the
invention. In FIG. 4, the eight non-planar shielding curtains 401,
402, 403, 404, 405, 406, 407, 408, each formed of a plurality of
slats 414, are arranged on a plurality of curtain supports 412 that
are coupled with a frame as described above. The slats 414 hang
suspended above a conveyor belt 416, which may move objects in
either direction indicated by the double-ended direction arrow 430.
Additionally, the eight strip curtains 401, 402, 403, 404, 405,
406, 407, 408 are nested. As used herein, "nested" refers to an
arrangement in which an apex of one strip curtain is positioned
between a base and apex of another longitudinally aligned strip
curtain, as illustratively shown in FIGS. 3 and 4. Depending on the
embodiment, two or more strip curtains may be nested in single or
multiple groupings. By way of example, FIG. 3 illustrates multiple
groupings of nested pairs of strip curtains, while FIG. 4
illustrates a single grouping of nested strip curtains. On the
other hand, the strip curtains illustrated in FIG. 2 would not be
considered nested since the apex of each succeeding strip curtain
is positioned outside of the base of the next adjacent strip
curtain.
[0052] Referring now to FIG. 5, a example of an inspection system
500 is shown with its housing and shielding curtains removed for
clarity. It will be appreciated that the embodiments of the
non-planar strip curtains described herein may be positioned
between the entrance 508 of the inspection system 500 and the
scanner 503, and between the scanner 503 and the exit 518 of the
inspection system 500.
[0053] The inspection system 500 may be configured to include one
or more of the new non-planar shielding curtains described herein.
The inspection system 500 includes a CT scanner 503 having a
rotatable gantry 502. As used herein, "inspection system" refers to
a machine having a scanner that scans an object to obtain scan data
that is characteristic of the object (and/or its contents), and/or
that analyzes the scan data using a computer to determine whether
the object comprises and/or contains one or more alarm objects.
[0054] The rotatable gantry 502 has an opening 504 therein, through
which packages or bags 516 may pass. The rotatable gantry 502
houses an x-ray source 506 as well as a detector assembly 508
having scintillator arrays comprised of scintillator cells. A
conveyor system 510 is also provided. The conveyor system 510
includes a conveyor belt 512 supported by structure 514 to
automatically and continuously pass packages or bags 516 to be
scanned through opening 504. Directional arrow 520 indicates the
direction in which the conveyor belt 512 rotates.
[0055] Objects 516 are fed through opening 504 by conveyor belt
512. Imaging data is then acquired, and the conveyor belt 512
transfers the packages 516 from the gantry opening 504 in a
controlled and continuous manner. As a result, inspectors, baggage
handlers, and other security personnel may non-invasively inspect
the contents of packages 516 for alarm objects. The term "alarm
object" refers to any substance or thing that an inspection system
is configured to detect. Non-limiting examples of alarm objects
include explosives, illegal drugs, hazardous substances, product
components, and the like. Additional aspects of the inspection
system 500 are described below with reference to FIGS. 5 and 6.
[0056] FIG. 6 is a block schematic diagram of a scanner that may be
used in an inspection system configured according to an embodiment
of the invention. Referring to FIGS. 5 and 6 together, the
inspection system 500 may be an explosive detection system that
includes an x-ray CT scanner. As used herein, "explosive detection
system" refers to a particular category of inspection system,
configured to detect explosives in baggage.
[0057] Referring again to FIGS. 5 and 6, the x-ray CT scanner
includes a circular, movable gantry 502. An x-ray source 506
attached to the gantry 502 projects a fan beam of x-rays 517 across
the interior of the gantry 502 to a detector array 508 that is also
attached to the gantry 502. The detector array 508 is formed by a
plurality of detector modules 521, which together sense the
projected x-rays that pass through an object 516. Each detector
module 521 comprises an array of pixel elements (pixels). Each
pixel comprises in part a photosensitive element, such as a
photodiode, and one or more charge storage devices, such as
capacitors. Each pixel produces an electrical signal that
represents the intensity of an impinging x-ray beam and hence the
attenuated beam as it passes through the object 516. During a scan
to acquire x-ray projection data, gantry 502 and the components
mounted thereon rotate about a center of rotation 524.
[0058] Rotation of gantry 502 and the operation of x-ray source 506
are governed by a control mechanism 526 of the inspection system
500. Control mechanism 526 includes an x-ray controller 528 that
provides power and timing signals to an x-ray source 506 and a
gantry motor controller 530 that controls the rotational speed and
position of gantry 502. A data acquisition system (DAS) 532 in
control mechanism 526 samples analog data from detectors 521 and
converts the data to digital signals for subsequent processing. An
image reconstructor 534 receives sampled and digitized x-ray data
from DAS 532 and performs high-speed reconstruction. The
reconstructed image is applied as an input to a computer 536, which
stores the image in a mass storage device 538.
[0059] Computer 536 also receives commands and scanning parameters
from an operator via console 540 that has a keyboard. An associated
display 542 allows the operator to observe the reconstructed image
and other data from computer 536. The operator supplied commands
and parameters that are used by computer 536 to provide control
signals and information to DAS 532, x-ray controller 528, and
gantry motor controller 530. In addition, computer 536 operates a
conveyor motor controller 544, which controls a conveyor belt 512
to position object 516 within the gantry 502. Particularly,
conveyor belt 512 moves portions of the object 516 through the
gantry opening 504.
[0060] FIG. 7 is a flowchart of an embodiment of a method 700 of
constructing a radiation shield. The method 700 may include a step
701 of gathering a plurality of slats of radiation attenuating
material. The gathering step 701 may include ordering,
constructing, and/or receiving one or more slats that each comprise
a radiation attenuating material. The method 700 may further
include a step 702 of disposing the slats to form a strip curtain
having a non-planar shape. The step 702 may include one or more
additional steps, such as, but not limited to: coupling each of the
slats with a curtain support; coupling each curtain support with a
frame, among other steps. The method 700 may further include a step
703 of positioning the strip curtain to cover an opening of a
scanner. The opening of the scanner may be an entrance opening or
an exit opening through which objects pass when traveling into or
out of a scanning area of the scanner.
[0061] The construction and arrangement of the curtain shielding
assembly, and/or an inspection system that includes an embodiment
of the curtain shielding assembly, as described herein and shown in
the appended figures, is illustrative only. Although only a few
embodiments of the invention have been described in detail in this
disclosure, those skilled in the art who review this disclosure
will readily appreciate that many modifications are possible (e.g.
variations in sizes, dimensions, structures, shapes and proportions
of the various elements, values of parameters, mounting
arrangements, use of materials, orientations, etc.) without
materially departing from the novel teachings and advantages of the
subject matter recited in the appended claims.
[0062] Accordingly, all such modifications are intended to be
included within the scope of the present invention as defined in
the appended claims. The order or sequence of any process or method
steps may be varied or re-sequenced according to alternative
embodiments. In the claims, any means-plus-function clause is
intended to cover the structures described herein as performing the
recited function and not only structural equivalents but also
equivalent structures. Other substitutions, modifications, changes
and omissions may be made in the design, operating conditions and
arrangement of the preferred and other exemplary embodiments
without departing from the spirit of the embodiments of the
invention as expressed in the appended claims.
* * * * *